Species

Introduction

Species is a type that stores information about a particle.

A species is defined by the following fields:

struct Species
    name   # name of the particle to track
    charge # charge of the particle
    mass   # mass of the particle
    spin   # spin of the particle
    moment # magnetic moment of the particle
    iso    # mass number of atomic isotope
    kind   # the kind of particle
end

The kind field classifies species into five types: ATOM, HADRON, LEPTON, PHOTON, and NULL. The NULL kind serves as a placeholder that can be used by Julia code. For example, if a struct has a Species component, a NULL species can be used as an initial value to indicate that the species component has not yet been set.

Each field stores values with their corresponding units and returns a Unitful value when accessed directly. For example:

julia> Species("electron").mass
0.51099895069 MeV c^-2

The default units are:

• mass: MeV/c²
• charge: elementary charge
• spin: ℏ
• moment: J/T

For convenience, use our getter functions massof() and chargeof() to obtain values in your preferred units. See the Constants page for more information.

Construct a Species

Use the constructor Species(name) to create a species.

Note: Species names follow the OpenPMD standard.

Constructing a Null species

The Null species is useful for bookkeeping purposes, such as a placeholder in a struct component to indicate an unset species. To instantiate:

julia> Species("Null")
julia> Species() # Same as above

Constructing Subatomic Species

To construct a subatomic species, provide the exact name of the particle in the name field. Note that the name must be provided exactly.

Example:

julia> Species("electron")

For antiparticles, prepend "anti-" to the name.

Example:

julia> Species("anti-proton")

See the list of all available subatomic species at the end of this page.

Constructing Atomic Species

To construct an atomic species, include these components in name:

• Atomic Symbol
• Mass number of the atom (optional), format:
  • Mass number before the atomic symbol (accepts unicode superscript)
  • Optional "#" symbol at the beginning
  • If not specified, uses the average of the mass in naturally occurring samples.
• These formats all represent Hydrogen-1:julia julia> Species("1H") julia> Species("¹H") julia> Species("#1H")
• Charge (optional), format (all accept unicode superscript):
  • "+" for single positive charge
  • "++" for double positive charge
  • "+n" or "n+" for n positive charges
  • "-" for single negative charge
  • "–" for double negative charge
  • "-n" or "n-" for n negative charges
  • Defaults to 0 if not specified
• Add "anti-" prefix to construct an anti-atom

Example:

julia> Species("13C+")   # Carbon-13 with a single positive charge
julia> Species("¹⁵N³⁻")  # Nitrogen-15 with a 3 negative charge
julia> Species("Al+3")   # Average Aluminum with 3 positive charge
julia> Species("anti-H") # Anti-hydrogen

Species Functions

Species functions each take a Species as their parameter and return a specific property. Here are the available functions:

• massof()
• chargeof()
• atomicnumber()
• fullname()
• g_spin()
  • $g = \frac{2m\mu }{Sq}$
  • $g$ is gyromagnetic ratio
  • $m$ is species mass
  • $\mu$ is the species magnetic moment
  • $S$ is the species spin
  • $q$ is the species charge
• gyromagnetic_anomaly()
  • $g_a = \frac{g-2}{2}$
  • $g_a$ is the gyromagnetic anomaly for a lepton
  • $g$ is the gyromagnetic ratio
• g_nucleon()
  • $g_n = \frac{g Zm_p}{m}$
  • $g_n$ is the gyromagnetic anomaly for a baryon
  • $g$ is the gyromagnetic ratio
  • $Z$ is the species charge
  • $m_p$ is the mass of a proton
  • $m$ is species mass

Note: You must call @APCdef before using massof() or chargeof().

List of Available Subatomic Species

• anti-deuteron

- anti-electron same as positron

• anti-neutron
• anti-proton
• anti-muon
• deuteron
• electron
• muon
• neutron
• photon
• pion0
• pion+
• pion-
• positron
• proton